Mold assemblies comprising two side mold parts and a base mold part are commonly used in the formation of plastic containers such as, for example, biaxially-oriented PET (polyethylene terephthalate) beverage bottles. The side mold parts may comprise a unitary half-part, multiple half-parts or a shell half insert. The base part of the mold assembly is typically manufactured from a steel adaptor plate and a cast steel or cut steel base insert that is inserted into the mold assembly.
The base insert is formed with a base mold face having a pattern or impression corresponding to the bottle to be formed. The adaptor plate is typically a cylindrical shaped plate to which the base insert is secured by threaded screws or bolts. The bolts pass through threaded apertures in the adaptor plate and into threaded apertures in the base insert. The adaptor plate acts to mount the base insert relative to a supporting pedestal assembly comprises a light weight base insert, preferably made from aluminum, having an upper surface containing the pattern of the base of the container to be formed. The light weight base insert is mounted to the adapator plate by the use of screws. A wear ring made from a hardened steel surrounds the base insert to protect and add strength to the light weight base insert.
Fluid circulating passages are machined into the adaptor plate and the base insert to assist in the cooling of the base mold part during the formation of the bottle. These passageways, as shown in the aforementioned U.S. Pat. No. 5,762,981, extend into the center of the adaptor plate, up into the base insert and then into a plurality of axially spaced apart radially extending outward passageways that pass back out through the adapter plate. These parallel radial flow passageways may not have equal flow of coolant there through, in practice, possibly resulting in non-uniform cooling of the mold base. Further, any blockage in one of the radial passageways may go undetected because the other passageways continue to function.